21891910 has 16 divisors (see below), whose sum is σ = 39586176. Its totient is φ = 8716608.

The previous prime is 21891907. The next prime is 21891911. The reversal of 21891910 is 1919812.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21891911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2679 + ... + 7138.

It is an arithmetic number, because the mean of its divisors is an integer number (2474136).

Almost surely, 2^21891910 is an apocalyptic number.

21891910 is a deficient number, since it is larger than the sum of its proper divisors (17694266).

21891910 is a wasteful number, since it uses less digits than its factorization.

21891910 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10047.

The product of its (nonzero) digits is 1296, while the sum is 31.

The square root of 21891910 is about 4678.8791392811. The cubic root of 21891910 is about 279.7442818351.

It can be divided in two parts, 21891 and 910, that added together give a square (22801 = 151²).

The spelling of 21891910 in words is "twenty-one million, eight hundred ninety-one thousand, nine hundred ten".